Illuminating unit for illuminating an original to be read by an image sensor

ABSTRACT

There is disclosed an image reading apparatus constructed by an illuminating unit for illuminating an object in a line shape, an image forming optical system for forming a light, as an image, from the object illuminated by the illuminating unit, a line sensor for converting the light formed as an image by the image forming optical system into an image signal, and a frame for holding the illuminating unit and the line sensor, wherein a shape in which vertices of at least a part of the cross section of the illuminating unit are connected by straight lines is set to a polygon of a pentagon or more, so that an image can be stably read at a high quality.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an image reading apparatus for reading anobject image and outputting an image signal.

2. Related Background Art

Hitherto, as shown in a cross sectional view of FIG. 11, an image sensorwhich is in contact with an original to be read and reads an image isconstructed by: an image sensor board 2 on which a sensor IC 1 isinstalled; a lens array 3 for guiding a reflected light from theoriginal illuminated by an illuminating unit 4 to the sensor IC 1; acover glass 5 which is come into contact with the original; and a frame6 for positioning and holding those component elements.

As an illuminating unit 4, a unit as shown in a cross sectional view anda top view of FIG. 12 is used. The illuminating unit 4 is constructedby: LEDs 7 of a lead frame type serving as light sources provided onboth ends; an optical guide member 8 arranged in a longitudinaldirection for converting a light irradiated from the LEDs into aline-shaped light; and a housing 9 having a square cross sectional shapefor positioning and holding the LEDs 7 and optical guide member 8. Anelectric power is supplied to the LED 7 from a power source (not shown)through a lead 11.

When such an illuminating unit 4 is attached to the frame, as shown inFIG. 11, in order to illuminate the light from the oblique direction of45° for the original, an attaching surface which is inclined by 45° forthe original mounting surface is provided for the frame 6, and thesurface corresponding to one side of a square in the cross section ofthe housing 9 constructing the illuminating unit 4 is come into contactwith the inclined attaching surface and is adhered by both-side adhesivetape or the like, thereby positioning and fixing.

However, in the conventional image sensor mentioned above, since thehousing of the illuminating unit having the square cross section isinstalled to the frame so as to be inclined by 45° for the originalsurface, there are the following problems.

(1) To enclose the illuminating unit into the frame, it is necessarythat a length of diagonal line in the cross section of the housing ofthe illuminating unit is assured in the vertical direction in the frame.However, the image sensor main body cannot be largely formed. Therefore,a thickness of frame with which the lower portion of the illuminatingunit is come into contact has to be made thin. It is difficult to workthe frame. Even if the frame can be worked, a mechanical strength of theframe is insufficient.

(2) An angle at which the illuminating unit is attached to the frame isnot equal to 45° depending on an individual difference of each imagesensor and an optical axis is deviated, so that there is a case where anilluminance on the original reading line doesn't reach a specifiedvalue.

(3) To fix the illuminating unit to the frame, not only a material suchas both-side adhesive tape or adhesive agent is necessary but also astep of attaching such a material is added, so that manufacturing costsrise.

SUMMARY OF THE INVENTION

It is an object of the invention to enable an image to be read at a highquality.

Another object of the invention is to provide an image reading apparatusof a high mechanical strength.

Still another object of the invention is to miniaturize an image readingapparatus.

Further another object of the invention is to suppress a variation inreading lines due to a deviation of an optical axis.

To accomplish the above objects, according to an embodiment of theinvention, there is provided an image reading apparatus comprising:illuminating means for illuminating an object in a line shape; imageforming optical system for forming a light, as an image, from an objectilluminated by the illuminating means; a line sensor for converting thelight formed as an image by the image forming optical system into animage signal; and holding means for holding the illuminating means andthe line sensor, wherein a shape formed by connecting vertices in atleast a part of a cross section of the illuminating means by straightlines is set to a polygon of a pentagon or more.

According to another embodiment, there is provided an image readingapparatus comprising: illuminating means which is constructed by a pointlight source and optical guide means for guiding and converting a lightfrom the point light source into a line-shaped light and illuminate anobject in a line shape; an image forming optical system for forming thelight, as an image, from the object illuminated by the illuminatingmeans; a line sensor for converting the light formed as an image by theimage forming optical system into an image signal; and holding means forholding the illuminating means and the line sensor, wherein at least apart of a cross section of the illuminating means has a circular shape.

According to still another embodiment, there is provided an imagereading apparatus comprising: illuminating means for illuminating anobject in a line shape; an image forming optical system for forming thelight, as an image, from the object illuminated by the illuminatingmeans; a line sensor for converting the light formed as an image by theimage forming optical system into an image signal; and holding means forholding the illuminating means and the line sensor, wherein at least apart of the cross sectional shape of the illuminating means has acircular shape and a convex portion is formed on the outer periphery ofthe circular shape and is come into engagement with a concave portionformed in the holding means, thereby certainly positioning.

According to further another embodiment, there is provided an imagereading apparatus comprising: illuminating means for illuminating anobject in a line shape; an image forming optical system for forming alight, as an image, from an object illuminated by the illuminatingmeans; a line sensor for converting the light formed as an image by theimage forming optical system into an image signal; and holding means forholding the illuminating means and the line sensor, wherein at least apart of the cross sectional shape of the illuminating means has acircular shape and a concave portion is formed on the outer periphery ofthe circular shape and is come into engagement with a convex portionformed in the holding means, thereby certainly positioning.

With the above construction, a cross sectional area of the illuminatingmeans is small and an enough mechanical strength can be assured whileminiaturizing the apparatus. Further, by certainly positioning theilluminating means, a variation in reading line can be suppressed and animage can be read at a high quality.

The above and other objects and features of the present invention willbecome apparent from the following detailed description and the appendedclaims with reference to the accompanying drawings.

BRIEF DESCRIPTION THE DRAWINGS

FIG. 1 is a cross sectional view of an image sensor according to thefirst embodiment;

FIG. 2 is a top view of an image sensor of the first embodiment;

FIG. 3 is a cross sectional view of an illuminating unit of the firstembodiment;

FIG. 4 is a side elevational view of an illuminating unit of the firstembodiment;

FIG. 5 is a detailed diagram of an optical guide member of the firstembodiment;

FIG. 6 is a cross sectional view of an image sensor according to thesecond embodiment;

FIG. 7 is a cross sectional view of an illuminating unit of the secondembodiment;

FIG. 8 is a side elevational view of an illuminating unit of the secondembodiment;

FIG. 9 is a cross sectional view of an image sensor according to thesecond embodiment;

FIG. 10 is a cross sectional view of an image sensor according to thesecond embodiment;

FIG. 11 is a cross sectional view of a conventional image sensor; and

FIG. 12 is a cross sectional view and a top view of a conventionalilluminating unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first embodiment of the invention will now be described hereinbelowwith reference to FIGS. 1 to 5. FIG. 1 is a cross sectional view of animage reading apparatus and FIG. 2 is a top view thereof.

The image reading apparatus according to the present embodiment isconstructed by: the image sensor board 2 in which a plurality of sensorICs 1 each having a group of line-shaped photoelectric convertingelements (line sensors) are accurately arranged on a board made of aglass epoxy material or the like in correspondence to a length oforiginal to be read; the lens array 3 serving as an image formingoptical system; the illuminating unit 4 serving as illuminating means;the cover glass 5 serving as supporting means for supporting an originaland made of a light transmitting material; and the frame 6 serving asholding means and made of a material of a metal such as aluminum or thelike or a resin such as polycarbonate or the like for positioning andholding the above component elements.

The original supported by the cover glass 5 is illuminated by a lightfrom the illuminating unit 4 from the oblique direction at an angle of45°. The reflected light from the original is formed as an image ontothe sensor IC 1 by the lens array 3. The sensor IC 1 converts lightinformation into an electric signal and transmits to a system imageprocessing unit.

FIG. 3 is a cross sectional view of the illuminating unit 4 and FIG. 4is a top view thereof.

As shown in FIGS. 3 and 4, the illuminating unit 4 is constructed by:the LEDs 7 serving as point light sources of the lead frame typeprovided as light sources at both ends; the optical guide member 8serving as optical guide means of a cylindrical shape and made of alight transmitting material such as an acrylic resin or the like inorder to guide the light of the LED in a line shape in the longitudinaldirection; and the housing 9 for positioning and holding the LEDs 7 andthe optical guide member 8. In the housing 9, a shape formed byconnecting vertices of a cross section by straight lines is a hexagon.

The LEDs 7 are provided on both ends of the optical guide member 8 andthe illumination light enters the optical guide member 8. A diffusingsurface 10 serving as a diffusing means is provided for the opticalguide member 8.

As shown in an enlarged diagram of FIG. 5, a fine tapered shape of thediffusing surface 10 is continuously formed in the longitudinaldirection of the optical guide member 8. The light entering at an anglesuch that an incident angle θ to the tapered portion is equal to orlarger than 41° (in the case where the optical guide member is made ofan acrylic resin and a refractive index n=1.5) satisfies the totalreflection conditions and is emitted in a desired direction.

The housing 9 for positioning and holding the LEDs 7 and the opticalguide member 8 has a slit 12 for transmitting the light to one side inthe direction where the light of the hexagonal cross section is emitted.In order to gain a light amount, the outside of the optical guide memberhas a white surface with a good light reflecting efficiency and is madeof a material such as an ABS resin or the like.

A method of manufacturing the image sensor will now be described.

The lens array 3 and illuminating unit 4 are inserted to predeterminedpositions of the frame 6, respectively. In the illuminating unit 4,three sides 9a, 9b, and 9c of the hexagon of the housing 9 shown in FIG.3 are respectively come into contact with a horizontal positioningsurface 6a and vertical positioning surfaces 6b and 6c of the frame 6shown in FIG. 1, thereby enabling the light source to be accuratelypositioned in the illuminating direction.

The cover glass 5 is adhered by an adhesive agent or the like onto twosurfaces 6d and 6e in the longitudinal direction of the frame 6 set soas to sandwich the illuminating unit 4 and lens array 3 on a plane thatis approximately the same as a top surface 9d of the housing 9 of theilluminating unit 4 inserted into the frame 6 and a top surface of thelens array 3.

The top surface 9d of the housing 9 of the illuminating unit 4 is ahorizontal surface and is in contact with the surface of the cover glass5 approximately in parallel, by adhering the frame 6 and cover glass 5,they can be fixed together with the illuminating unit 4. By insertingthe sensor array 2 into the frame 6 and fixing with an adhesive agent orthe like, the apparatus is completed.

According to the embodiment as described above, since the shape in whichthe vertices of the cross section of the housing of the illuminatingunit are connected by straight lines is a hexagon, the cross sectionalarea of the housing can be reduced and the frame of a thickness with anenough mechanical strength can be assured. Further, since a sittingstate of the illuminating unit to the frame is improved, a deviation ofthe optical axis can be prevented and a variation in illuminances of theoriginal reading lines among the products can be suppressed. By adheringthe frame and the cover glass, the illuminating unit can be alsosimultaneously fixed. The assembling steps can be simplified and thecosts can be reduced.

Although the embodiment has been shown and described with respect to theexample in the case where the shape in which the vertices of the crosssection of the housing of the illuminating unit are connected bystraight lines is a hexagon, the invention is not limited to such anexample. By setting such a shape to a polygon of a pentagon or more, asimilar effect can be obtained.

FIGS. 6, 7, and 8 show an image reading apparatus of the secondembodiment. Since a construction of the image reading apparatus of thesecond embodiment is fundamentally similar to that of the firstembodiment, the description of the same portions is omitted here.

The optical guide member 8 in the embodiment has a cylindrical orelliptic cylindrical shape or a shape similar thereto. In order tominimize a volume of illuminating unit 4, it is desirable that a crosssectional shape of the housing 9 has a circular or an elliptic shape ora shape similar thereto in correspondence to the optical guide member 8.On the other hand, when the shape of the housing 9 is set to a simplecylindrical or elliptic cylindrical shape, when it is attached to theframe 6, the position in the optical axial direction is not determined.

In the embodiment, therefore, although the housing 9 has a cylindricalshape, convex portions 13 are formed on both ends of the housing 9.Concave portions 14 are formed in the frame 6 so that the convexportions 13 are fitted into the concave portions 14. By inserting theconvex portions 13 into the concave portions 14, the position in theoptical axial direction and the position in the longitudinal directioncan be simultaneously determined. With respect to the foregoing firstembodiment as well, by forming the convex portions 13 in the housing 9and by inserting the convex portions 13 into the concave portions 14 ofthe frame 6 as shown in FIG. 9 in a manner similar to the secondembodiment, the positioning in the longitudinal direction can becertainly executed. In the embodiment, although the convex portions havebeen formed in the housing, by forming convex portions 15 in the frameand forming concave portions 16 in the housing as shown in FIG. 10, asimilar effect is derived.

Further, although the shape of the equal magnification optical systemhas been described in the above embodiments, the invention can be alsoobviously applied to the image sensor using a reduction magnificationoptical system.

Many widely different embodiments of the present invention may beconstructed without departing from the spirit and scope of the presentinvention. It should be understood that the present invention is notlimited to the specific embodiments described in the specification,except as defined in the appended claims.

What is claimed is:
 1. An image reading apparatus comprising:(A)illuminating means held in a housing, for illuminating an object in aline shape; (B) an image forming optical system for forming a light, asan image, from the object illuminated by said illuminating means; (C) aline sensor for converting the light formed as an image by said imageforming optical system into an image signal; and (D) holding means forholding said housing and said line sensor,wherein a shape of a crosssection of said housing is a polygon having at least five sides.
 2. Anapparatus according to claim 1, wherein said illuminating means ispositioned in a manner such that at least three sides of said housingand said holding means come into contact with said holding means.
 3. Anapparatus according to claim 1, wherein said illuminating means includesa point light source and optical guide means for guiding the light fromsaid point light source and converting said light into a line-shapedlight.
 4. An apparatus according to claim 3, wherein said illuminatingmeans further includes diffusing means for illuminating the lightconverted in the line-shaped light by said optical guide means in apredetermined direction.
 5. An apparatus according to claim 4, whereinsaid diffusing means has a stairway-shaped diffusing surface.
 6. Anapparatus according to claim 3, wherein said housing holds said pointlight source and said optical guide means.
 7. An apparatus according toclaim 6, wherein said housing has a slit in the illuminating directionof the light.
 8. An apparatus according to claim 1, further comprisingsupporting means for supporting said object, and wherein by adhering alower surface of said supporting means onto a top surface of saidholding means, said illuminating means is fixed.
 9. An apparatusaccording to claim 8, wherein said supporting means is a lighttransmitting member.
 10. An image reading apparatus comprising:(A)illuminating means held in a housing, for illuminating an object in aline shape, said illuminating means includes an optical guide means anda light source arranged at an end of said optical guide member; (B) animage forming optical system for forming a light, as an image, from theobject illuminated by said illuminating means; (C) a line sensor forconverting the light formed as an image by said image forming opticalsystem into an image signal; (D) holding means for holding said housingand said line sensor,wherein a concave portion is formed on a part ofsaid illuminating means and said concave portion comes into engagementwith a convex portion formed in said holding means.
 11. An apparatusaccording to claim 10, wherein said illuminating means further includesdiffusing means for illuminating the light in a predetermined direction.12. An apparatus according to claim 11, wherein said diffusing means hasa stairway-shaped diffusing surface.
 13. An apparatus according to claim11, wherein said housing holds said point light source and said opticalguide means.
 14. An apparatus according to claim 13, wherein saidhousing has a slit in the illuminating direction of the light.
 15. Anapparatus according to claim 10, further having supporting means forsupporting said object, and wherein by adhering a lower surface of saidsupporting means onto a top surface of said holding means, saidilluminating means is fixed.
 16. An apparatus according to claim 15,wherein said supporting means is a light transmitting member.
 17. Anapparatus according to claim 10, wherein at least a part of a crosssectional shape of said illuminating means is an elliptic shape.
 18. Animage reading apparatus comprising:(A) illuminating means held in ahousing, for illuminating an object in a line shape, said illuminatingmeans includes an optical guide means and a light source arranged at anend of said optical guide means; (B) an image forming optical system forforming a light, as an image, from the object illuminated by saidilluminating means; (C) a line sensor for converting the light formed asan image by said image forming optical system into an image signal; (D)holding means for holding said housing and said line sensor,wherein aconvex portion is formed on a part of said illuminating means and saidconvex portion comes into engagement with a concave portion formed insaid holding means.
 19. An apparatus according to claim 18, wherein saidilluminating means further includes diffusing means for illuminating thelight in a predetermined direction.
 20. An apparatus according to claim19, wherein said diffusing means includes a stairway-shaped diffusingsurface.
 21. An apparatus according to claim 19, wherein said housingholds said point light source and said optical guide means.
 22. Anapparatus according to claim 21, wherein said housing has a slit in theilluminating direction of the light.
 23. An apparatus according to claim18, further comprising supporting means for supporting said object, andwherein by adhering a lower surface of said supporting means onto a topsurface of said holding means, said illuminating means is fixed.
 24. Anapparatus according to claim 23, wherein said supporting means is alight transmitting member.
 25. An apparatus according to claim 18,wherein at least a part of a cross sectional shape of said illuminatingmeans is an elliptic shape.